Research Of Bioflocculant On Screening Of Microbes, Optimization Of Growth Conditions And Applications

With properties of high flocculating efficiency, without toxicity and second pollution,self-degradability and wild application, the research on development and application ofbioflocculant has been a focus of the area of biological preparation in recent years. For thepurpose of obtaining micro flocculant with low cost and high efficiency and exploring theprobability for large scale industrial manufacture of micro flocculant, a series of researcheswere carried out from screening of microbes with flocculating ability to batch fermentationof bioflocculant in this paper. First of all, four kinds of flocculating microbes with goodflocculating ability which were B-04,B-20,B-47 and M-03 were obtained by enrichment,first selection and reselection from three kinds of activated sludges. The morphology ofthese four microbes was observed by coloration. And these flocculating microbes werecultivated with low-cost fish-blood culture medium, getting the result of presenting fairlygood flocculating ability after the cultivation, which indicated that the fish-blood culturemedium can be used as substitute culture medium for cultivation of flocculating microbes.The flocculating ability under different flocculating conditions were determined, includingpH of solution, length of sedimentation time, disposal of high temperature, volumes of thesolution of coagulant aid and volumes of the supernatant of flocculating microbes. Theresults showed that the flocculating microbes presented higher flocculating ability underalkaline environment and with longer sedimentation time;there were sugar contained inthe microbes, as the flocculating ability were not decreased and increased on the contraryafter treatment with high temperature. Moreover, the optimal volumes of solution ofcoagulant aid and supernatant of flocculating microbes were got. After that, theflocculating microbe B-20 was induced under hit and UV radiation consecutively. B-2022obtained after hit inducing and B-202225 got after UV radiation both showed higherflocculating ability compared with B-20. L₉(3⁴) orthogonal experiments were carried out toresearch the influence of the change in initial pH of culture medium, culture temperatureand rotating speed of shaker on the flocculating ability of the four microbes in order toimprove the flocculating activity by the improvement of growth conditions. Further more,single factor experiment was carried out on B-04. The growth curves of cells of thesemicrobes as well as the flocculating ability and pH of culture medium in different culturetime were determined. Batch cultivation of B-04 was carried out for applying theflocculating bacteria into industry, and three rate models of the development of bacteria,the consumption of carbon and the production of flocculating agent were got according tothe experimental data. For the purpose of a deeper understanding of the chemicalcharacteristics and the flocculating mechanism of B-04, some chemical experiments were carried out by extracting the flocculating agent BEF-14 from B-04, determining the content of sugar and protein in BEF-14 and the UV and infrared spectrum map of BEF-14. The analysis to these chemical characteristics indicated primarily that sugar is the main flocculating substance in B-04. The practical application effect of these four microbes were also determined in this paper, including the removal ability to chroma, turbidity and COD of dye solution, active carbon solution and simulated wastewater solution. The results showed that the flocculating rates of these four microbes to COD of dye solution were all more than 80%, and that of B-04 to chroma and turbidity of active carbon solution and COD of simulated wastewater solution were all more than 95%. The whole experiment developed the flocculating microbe B-04 with high flocculating ability and viscidity, researched the probability of industrial production and application of B-04 primarily, produced B-04 cosmically by batch cultivation and applied B-04 in the removal of grain suspend, chroma, turbidity and COD of industrial wastewater. The good flocculating ability and stable propagating capability of B-20, B-47 and M-03 also provided reliable assurance for their industrial production and application.